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/**
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* Back 2 Browser Bytecode Translator
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* Copyright (C) 2012 Jaroslav Tulach <jaroslav.tulach@apidesign.org>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 2 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. Look for COPYING file in the top folder.
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* If not, see http://opensource.org/licenses/GPL-2.0.
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*/
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package org.apidesign.vm4brwsr;
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import java.io.IOException;
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import java.io.InputStream;
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import java.net.URL;
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import java.util.Enumeration;
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/** Build your own virtual machine! Use methods in this class to generate
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* a skeleton JVM in JavaScript that contains pre-compiled classes of your
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* choice. The generated script defines one JavaScript method that can
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* be used to bootstrap and load the virtual machine: <pre>
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* var vm = bck2brwsr();
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* var main = vm.loadClass('org.your.pkg.Main');
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* main.main__V_3Ljava_lang_String_2(null);
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* </pre>
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* In case one wants to initialize the virtual machine with ability to
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* load classes lazily when needed, one can provide a loader function to
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* when creating the virtual machine: <pre>
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* var vm = bck2brwsr(function(resource) {
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* return null; // byte[] for the resource
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* });
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* </pre>
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* In this scenario, when a request for an unknown class is made, the loader
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* function is asked for its byte code and the system dynamically transforms
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* it to JavaScript.
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*
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* @author Jaroslav Tulach <jtulach@netbeans.org>
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*/
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public final class Bck2Brwsr {
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private Bck2Brwsr() {
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}
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/** Generates virtual machine from bytes served by a <code>resources</code>
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* provider.
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*
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* @param out the output to write the generated JavaScript to
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* @param resources provider of class files to use
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* @param classes additional classes to include in the generated script
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* @throws IOException I/O exception can be thrown when something goes wrong
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*/
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public static void generate(Appendable out, Resources resources, String... classes) throws IOException {
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StringArray arr = StringArray.asList(classes);
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arr.add(VM.class.getName().replace('.', '/'));
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VM.compile(resources, out, arr);
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}
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/** Generates virtual machine from bytes served by a class loader.
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*
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* @param out the output to write the generated JavaScript to
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* @param loader class loader to load needed classes from
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* @param classes additional classes to include in the generated script
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* @throws IOException I/O exception can be thrown when something goes wrong
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*/
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public static void generate(Appendable out, final ClassLoader loader, String... classes) throws IOException {
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class R implements Resources {
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@Override
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public InputStream get(String name) throws IOException {
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Enumeration<URL> en = loader.getResources(name);
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URL u = null;
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while (en.hasMoreElements()) {
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u = en.nextElement();
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}
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if (u == null) {
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throw new IOException("Can't find " + name);
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}
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return u.openStream();
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}
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}
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generate(out, new R(), classes);
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}
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/** Provider of resources (classes and other files). The
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* {@link #generate(java.lang.Appendable, org.apidesign.vm4brwsr.Bck2Brwsr.Resources, java.lang.String[])
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* generator method} will call back here for all classes needed during
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* translation to JavaScript.
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*/
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public interface Resources {
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/** Loads given resource (class or other file like image). The
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* resource name to load bytes for the {@link String} class
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* would be <code>"java/lang/String.class"</code>.
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*
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* @param resource path to resource to load
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* @return the input stream for the resource
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* @throws IOException can be thrown if the loading fails on some error
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* or the file cannot be found
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*/
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public InputStream get(String resource) throws IOException;
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}
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}
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